This invention relates to control valves and particularly to a valve for controlling refrigerant temperature at the compression stage of a refrigeration system.
For environmental reasons the refrigerant currently used with refrigeration systems is being changed to R-22 for low and medium temperature applications. This requires little or no change in equipment for medium temperature applications but in low temperature applications the compression ratio of a single stage compressor causes high discharge temperatures.
One solution to the problem is to provide two stage compression but this tends simply to change the location of the problem to the high stage compressor. Another solution is to apply a conventional expansion valve, set at a relatively high superheat setting, to the suction inlet of the compressor which injects liquid into the suction inlet which reduces the superheat of the compressor discharge gas. This method, in effect, measures and controls one parameter (suction temperature) to control another parameter (discharge temperature).
Another method of controlling the temperature of the discharge gas is to measure its temperature at the compressor head by determining the temperature of the discharge gas by means of a temperature sensor, reading the temperature with a solid state control and injecting liquid through a small solenoid valve into the head of the compressor. This approach is expensive and requires drilling inlet holes in the head of the compressor.
The present invention utilizes a liquid injection approach but without the need for direct modification of the compressor.